The present invention relates to a system for recording or reproducing a signal under tracking control. A light beam, generated from a light source and irradiated by being focused on a record carrier, constantly scans the track. More specifically, a track jump detection system detects any track jump which may occur during the recording of a signal on a record carrier or during a reproduction thereof from the record carrier.
An invention related to this type of system is disclosed, for example, by JP-A-No.-59-11546.
In this prior art system, a signal from a track displacement detector is used to detect a track jump of a light beam on a record carrier, and in the case of a track jump that may occur during recording, the light quantity of the light beam is immediately reduced.
According to this prior art system, the light quantity of the light beam sharply increases immediately after starting the recording, often causing a disturbance in the output signal of the track displacement detector, with the result that a track jump is liable to be assumed to stop the recording even when there is no excessive track displacement or track jump occuring.
In the case of a record carrier which, once recorded, cannot be erased for reuse, suspension of the recording makes it impossible to use the particular recording region again, thus reducing the recording capacity.
Even in the case of a record carrier in which the same region can be used for recording after erasure, it takes considerable time for erasure and renewed recording, thereby greatly reducing the data processing speed of the system.
In conventional systems, a track jump associated only with the recording operation is detected, so that a track jump that may occur during reproduction is left unrecognized by the data processing control means and is transmitted directly to devices connected with the system.
In the case of a system device in which image signals recorded on a record carrier are searched for a desired image to be displayed on a monitor, for instance, an erroneous image is undesirably displayed as a result of a track jump.
There is a system in which a track is divided into a multiplicity of sectors capable of recording data of predetermined capacity, and each sector is recorded in advance with an index signal for the purpose of recording or reproducing a signal on the recording carrier. In such a system, when the index signal cannot be read, it is impossible to determine whether the unreadability is attributable to a track jump or a defect of the particular index signal due to a flaw or the like, thus complicating the system processes while at the same time reducing the processing speed.
The recording carrier has a multiplicity of flaws or drop-outs thereon. Conventional systems regard even a minor flaw that poses no problem of track jump for recording or reproducing as a track jump, sometimes leading to a stop of the recording operation for a reduced recording capacity of the record carrier.